1. Statement of the Technical Field
The inventive arrangements relate to portable radios, and more particularly to maximizing transmitter power output of portable handheld radio equipment.
2. Description of the Related Art
Improvements in technology have led to the development of a new generation of multi-band portable radios. These portable radios include multi-mission tactical radios that are designed to be compatible with the Joint Tactical Radio System (JTRS). The JTRS system is built upon the well known Software Communications Architecture (SCA) which establishes a system by which programmable radios can be quickly modified with software to implement any one of a wide variety of communication link protocols on a variety of frequency bands. These highly flexible radios are capable of operating over a very wide range of frequencies, for communicating voice and data using any one of a variety of modulation schemes.
Notwithstanding the highly flexible software defined nature of these radios, there remain certain aspects of the equipment that must be implemented in hardware. This hardware typically includes the transmitter RF power amplifier circuitry. The hardware nature of this circuitry has typically resulted in certain compromises. For example, since the nature of the transmitted signals is programmable, the transmitter power amplifier circuitry must be designed to accommodate any communications protocol, regardless of frequency, waveform, modulation, data rate, and duty cycle. While this approach ensures flexibility, it is necessarily a compromise design.
For example, the transmitter output power can be limited to protect the final RF power amplifier under worst case conditions. This is typically implemented at design time by fixing various circuit parameters, such as the voltage applied to the power amplifier, transistor bias current settings, and maximum power output. While necessary to protect the RF power amplifier, these fixed design parameters can limit the maximum transmitter performance achievable under certain circumstances. For example, an RF power amplifier can be designed for a maximum 5 watt output power. This design can protect the power amplifier from damage caused by overheating. Under certain limited circumstances it may be possible to safely increase power amplifier RF power output levels. However, because the RF power amplifier design must be compatible with any communication protocol, the more conservative circuit design must be implemented.